The present invention is particularly applicable to hydraulic material handling machinery and it will be discussed with particular reference thereto; however, the invention has much broader applications and can be used with rippers, shears, pile drivers, crushers, etc. Hydraulic cylinders are used on many types of equipment such as front end loaders, backhoe buckets, digging buckets, and various other material handling devices. For each one of these applications, a hydraulic cylinder moves a particular component such as a bucket into position during operation. The size of the equipment is based upon the expected load or force needed to carry out the particular operation. Upon determining the expected load, the size of the equipment can be selected which can operate within the expected load requirements. A typical hydraulic cylinder includes a main cylinder housing having a central cavity and a hole passing through the housing and intersecting the central cavity. Within the central cavity is a cylinder rod having a rodhead section and a rodend section wherein the cross-sectional area of the rodhead section is generally larger than the cross-sectional area of the rodend section. The cylinder rod within the cylinder central cavity is typically moved by hydraulic liquid fluid applied to the base or top of the rodhead. The cylinder rod could also be moved by gases, a mechanical spring or a combination of liquid, gas and/or a mechanical mechanism. The hydraulic cylinder includes a valve system which directs hydraulic fluid within the cylinder central cavity to move the cylinder rod within the cylinder central cavity. The hydraulic cylinder is made of standard materials such as steel, stainless steel or plastic; however, other materials could be used. The type of material and the thickness of the cylinder material determines the maximum pressure rating for a particular hydraulic cylinder. The cylinder housing and central cavity typically have a generally circular cross-sectional area; however, other shapes can be used. The cross-sectional area of the cylinder rod is usually the same cross-sectional shape as the cylinder central cavity to facilitate the movement of the cylinder rod within the cylinder central cavity. The maximum amount of pressure which can be applied to the cylinder rod determines the maximum load the hydraulic cylinder can move during operation. For hydraulic equipment, the load determining factors for a particular piece of equipment is usually based upon the maximum load rating of the hydraulic cylinder and the pressure limit of the seals. The force applied by standard hydraulic cylinders is limited to the strength of the cylinder housing, the size of the cylinder piston and the maximum pressure which can be applied to the cylinder piston. During the operation of a piece of equipment, if the loads encountered by the equipment exceed the maximum load rating of the hydraulic cylinder, the equipment would have to be exchanged for larger equipment or the undersized hydraulic cylinder will be overstressed leading to excessive wear and possible failure. Such situations arise during the excavation of land wherein an unexpected obstacle, such as a layer of rock, is encountered. In the past, a larger piece of equipment would have to be employed to break through the rock layer. In order to avoid the delay necessary to obtain larger equipment, oversized equipment would have to be used. For most of the job, the larger equipment is oversized. Such larger equipment is much more costly to operate and obtain. Furthermore, due to the larger size of the equipment, the equipment is harder to move, maneuver and/or store. As a result, there is a demand for hydraulic equipment which includes a hydraulic cylinder which operates as a standard hydraulic cylinder within expected operation conditions and can supply additional force to overcome unexpected loads which exceed normal operating conditions.
These and other problems are overcome by the present invention wherein a hydraulic cylinder is integrated with a hydraulic impact hammer wherein the impact hammer acts upon the hydraulic cylinder piston when the cylinder piston encounters a load which exceeds normal operating conditions.